Actually i want to know that if a keyword has 10000 searches in a month then how much traffic i get from this keyword if my website is rank on top 3 for that.

Only one way to know..get in the top 3 and analyze your stats. Knowing #1 will get a lot more than 2 and so on.
This may help answer your question here Don't know how spot on that is but it'll help give you some idea.

Yeah... I'd make your first goal to get into the top 3 first, and then worry about traffic volumes. That first goal will keep you busy for a while!

It's fair to say that if you rank highly for a keyword with a lot of monthly searches, you'll probably see a decent amount of traffic from it. I can't see how Google would rank you highly if you weren't relevant to the keyword, which means people will be likely to click through to you. Make that your focus: Picking keywords that are relevant to your site, and produce content or pages that are super relevant to those keywords.

Also it's not just about monthly searches and traffic when you pick your keywords. You also have to consider competition. If a keyword has a lot of monthly competition but a lot of big players vying for the top spots, you're unlikely to rank high enough to see much traffic anyway.

All you can do when you're starting is look into the best keywords while keeping in mind that you want high search volume, low competition, relevance to your website and some long-tail options. Best of luck with your research.